1. Field of the Invention
The present invention relates to a method and apparatus for dressing a polishing pad on a polishing table by pressing a dresser against the polishing pad, and also relates to a polishing pad profile measuring method, a substrate polishing apparatus, and a substrate polishing method.
2. Description of the Related Art
Recent progress in high integration of semiconductor devices results in smaller wiring patterns and narrower distances between interconnects. Photolithography is one of the device fabrication processes. In this photolithography, a stepper requires a highly flat image plane, particularly when forming interconnects of at most 0.5 μm wide, because a depth of focus is small. Thus, a polishing apparatus, which performs Chemical Mechanical Polishing (CMP), is used for planarizing a surface of a semiconductor wafer.
Conventionally, as shown in FIG. 1, a polishing apparatus of this type typically includes a polishing table 102 holding, on its upper surface, a polishing pad (or a polishing cloth) 100 that provides a polishing surface, and a top ring 104 for holding a substrate (e.g., a semiconductor wafer) W which is a workpiece to be polished. The top ring 104 rotates the substrate W and presses the substrate W against the polishing pad 100 on the rotating polishing table 102 at constant pressure, while a nozzle 106 supplies a polishing liquid onto the polishing pad 100, to thereby polish a surface of the substrate W to flat mirror finish. Examples of the polishing liquid to be used include an alkaline solution with abrasive grains, such as fine particles of silica, suspended therein. With use of such polishing liquid, the substrate W is chemically and mechanically polished by a combination of a chemical polishing action of the alkaline solution and a mechanical polishing action of the abrasive grains.
The polishing apparatus also has a dressing apparatus disposed adjacent to the polishing table 102. This dressing apparatus includes a dresser 108 for restoring the polishing surface of the polishing pad 100 that has been deteriorated through the polishing process. The dresser 108 is configured to rotate about its own axis and bring a dressing surface thereof into contact with the polishing surface of the polishing pad 100 on the rotating polishing table 102 to thereby remove the polishing liquid and debris on the polishing surface and also planarize and dress the polishing surface of the polishing pad 100. Typically, a diamond dresser is used as the dresser 108 for scraping and planarizing the polishing surface of the polishing pad 100. A uniformity of the dressed polishing surface greatly affects polishing accuracy in subsequent polishing processes of substrates.
When the dresser 108 is replaced with a new dresser, the following problems may arise. Since individual dressers have different properties, the new dresser can have a different cutting rate of the polishing pad. As a result, a removal rate and a polishing profile may change. After the dresser 108 is replaced with a new dresser, preconditioning of the new dresser is usually performed by pressing the new dresser against the polishing pad 100 at given pressure. This preconditioning process is, however, problematic because it may adversely affect a polishing performance at an initial stage of polishing the substrate W. In addition, a slurry, that has been removed by the dressing process, may be deposited firmly on the dresser 108, and may adversely affect a stability of the polishing performance.